ksmbd: fix slab-use-after-free in smb2_lock

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Author: namjaejeon

smb2pdu.c

@@ -8059,13 +8059,13 @@ int smb2_lock(struct ksmbd_work *work)
 		}
 
 no_check_cl:
+		flock = smb_lock->fl;
+		list_del(&smb_lock->llist);
+
 		if (smb_lock->zero_len) {
 			err = 0;
 			goto skip;
 		}
-
-		flock = smb_lock->fl;
-		list_del(&smb_lock->llist);
 retry:
 		rc = vfs_lock_file(filp, smb_lock->cmd, flock, NULL);
 skip: